Method for the detection of cancer cells by localization of peptides in nucleus as compared to cytoplasm

ABSTRACT

The human LIV21 protein as a diagnostic and prognostic marker for various cancers and neurodegenerative diseases is provided. Methods for diagnosing and/or prognosing cancer utilizing the LIV21 protein and various derivatives and peptide fragments of the LIV21 protein are also provided.

FIELD OF THE INVENTION

The present invention relates to the field of medicine and biology. It concerns a novel test for screening and for therapeutic follow-up in oncology. More particularly, it relates to diagnostic and/or therapeutic tests in oncology and on neurodegenerative diseases.

BACKGROUND OF THE INVENTION

Age-related neurodegenerative diseases and cancers both involve a modification of the physiological process of programmed cell death or apoptosis. Neuronal death is abnormally accelerated during neurodegenerative diseases such as Alzheimer's disease,

Huntington's disease, Parkinson's disease, etc. On the other hand, the cancerization process corresponds to a blocking of apoptosis which results in an uncontrolled multiplication of cells. The link between these two processes has currently become a major field of investigation in research on aging.

The control of the balance between cell division (mitosis), differentiation and programmed cell death (apoptosis) is fundamental during normal physiological processes, such as embryonic development, tissue regeneration and aging. An impairment of this balance can lead to major pathological situations such as the formation of tumors or certain neurodegenerative diseases.

Cancer is one of the principal causes of mortality throughout the world. Although, over the course of the last generation, the percentages of deaths related to cardiac and cardiovascular diseases and a large number of other diseases has decreased, the number of deaths related to the various forms of cancer is on the increase.

Despite the rapid advance in our understanding of the various forms of cancer, the low survival rates can generally be attributed to inadequate diagnosis and inadequate treatment.

Most tumors can only be detected when they reach a size of approximately 1 cm. Since there is a relatively short period of time from the continuous development of a tumor to a stage which has become incompatible with survival, this leaves little time for a therapeutic intervention. Early diagnosis therefore becomes the key to success for the treatment of cancer.

For a multitude of reasons, early diagnosis remains illusory for most forms of cancer. For certain forms of cancer, disease-specific markers are not available or are only available at an advanced stage of the disease, making diagnosis difficult. In certain other forms of cancer, the markers are available but are not always specific for the disease or they may be associated with its benign form. In yet other cases, the techniques exist but the prohibitive cost for applying them to the population in general makes them unsuitable.

Skin cancer, for example, is the most widespread cancer in Canada. In 1992 alone, 50 300 new cases of skin cancer were reported, compared with 19 300 cases of lung cancer, 16 200 cases of colorectal cancer and 15 700 cases of breast cancer. In other words, skin cancer is as common as the three main types of cancer combined. Its incidence continues to increase, with 64 200 new cases thereof in 1997, that is an increase of 14 000 cases annually in 5 years. In particular, the incidence of malignant melanoma is increasing at a rate of 2% per year. Early diagnosis remains the key to an effective treatment. A malignant tumor is readily accessible and can be removed with minor surgery. In fact, recovery is 100% if skin cancer is detected early enough. The early diagnosis of skin cancer remains, however, difficult. The latter is not just one disease but an entire range of conditions related to one another, which appear similar in many cases upon visual inspection. A diagnosis on the basis of such an inspection is therefore subjective. In order to understand this subjectivity more fully, an abnormal skin growth should be considered. This growth may be pigmented or nonpigmented. If it is nonpigmented and malignant, it is then probably a basocellular epithelioma or a spinocellular epithelioma. However, the clinical development of these two forms of cancer is very different. A basocellular epithelioma spreads out laterally over the surface of the skin, without penetrating into the deeper skin layers. Thus, although it can be disfiguring, a basocellular epithelioma rarely develops metastases and is rarely fatal. However, a spinocellular epithelioma causes metastases and is often fatal. It therefore becomes important to be able to distinguish these two types of skin cancer. A definitive diagnosis of skin cancer requires a biopsy and histological analysis. However, the decision to send a biopsy for analysis (or even whether a patient should be referred to a dermatologist) becomes very subjective. There are several biopsies which are not taken although they should have been.

Colon cancer is the third most common cause of cancer-related mortality in men and women in North America (16 200 cases per year). Early detection, leading to an early intervention, has demonstrated that treatment success and survival rate can be improved. For example, the 5-year survival rate is 92% for a patient whose disease was detected at an early stage, whereas the rate drops to approximately 60% in patients with a localized cancer, and to approximately 6% in those with metastases. However, only a third of colon cancers are detected at an early stage. One of the reasons for this delay in diagnosis is the absence of a sensitive, relatively inexpensive, noninvasive screening test.

Breast cancer is one of the most common cancers in women, with colon cancer. The mortality rate is the highest of all the cancers affecting women. There are very few diagnostic markers capable of detecting breast cancer and they only have a predictive value of 20%. There are no markers, either, which can detect or determine the invasiveness or the aggressiveness of metastatic cancer cells.

Over the last few years, considerable progress has been made in the understanding of the means used by oncogenes and tumor suppressor genes for regulating cell proliferation and apoptosis. One of the main targets of these regulators is the family of E2F-type transcription factors in the E2F and RB protein signaling pathway. These proteins play a central role in controlling cell division by coupling the regulation of the genes required for progression of the cell cycle with extracellular signals (mitogens, proliferation inhibitors) It behaves as an oncogene by stimulating tumor cell proliferation.

Among the expressed genes are found:

-   -   overexpression of the E2F4 transcription factor and the c-myc         oncogene which induce apoptosis of post-mitotic cells by         accumulation of oxygenated reactants (Tanaka, 2002);     -   the p53 gene, which belongs to the tumor suppressor gene family,         blocks the cell cycle in the case of DNA lesion. It has now been         demonstrated that this gene is also involved in the progression         of apoptosis (Oren, 1994; Yonish-Rouach, 1996);     -   the cyclin Dl, one of the proteins constituting the regulatory         subunits of the kinases of the cell cycle, essential to the         progression of the cell cycle. This protein is also expressed         during apoptosis in various cell types (Han et al, 1996; Pardo         et al, 1996).

It would be desirable to have novel diagnostic methods which would detect the presence of cancer with greater specificity and which would make it possible to distinguish between aggressive cancer cells having a tendency to metastasize and those which are more localized which have a lower probability of metastasizing. A marker which can therefore reveal cell proliferation would be of great use.

SUMMARY OF THE INVENTION

The present invention concerns a novel test for screening for reinduction of the cell cycle targeting oncology. It is a diagnostic test and a prognostic test for various cancers (breast cancer, bladder cancer, ovarian cancer, lung cancer, skin cancer, prostate cancer, colon cancer, liver cancer, glioblastoma, sarcoma, leukemia, etc.). More particularly, the invention concerns the use of the LIV21 protein and of derivatives thereof as diagnostic and prognostic markers for cancers. The invention therefore concerns the detection of the LIV21 protein with a kit comprising LIV21-specific antibodies.

A first objective of the present invention is to demonstrate a method for the detection and prognosis of cancer and of its metastatic potential. Preferably, the cancer is selected from breast cancer, bladder cancer, ovarian cancer, lung cancer, skin cancer, prostate cancer, colon cancer, liver cancer, a sarcoma, a leukemia and glyoblastoma, without being limited thereto.

One aspect of the present invention consists of the use of LIV21 as a prognostic indicator for cancer. In fact, when LIV21 is located in the cytoplasm, the cancer cells in the tissues are aggressive. Conversely, when the LIV21 gene expression product is preferentially located in the cell nucleus, this is a prognostic indicator that the cells of the tissue are differentiated and quiescent and therefore noninvasive. The effectiveness of a cancer treatment can also be monitored by the traceability of this protein, and of its derivatives and ratios with the associated proteins.

Moreover, detection of protein kinase C epsilon (PKCE) is also advantageous since it has been determined that PKCE phosphorylates the LIV21 protein in order to maintain it in the cytoplasm. Thus, a significant increase in PKCE is indicative of the presence of cancer cells. Moreover, the LIV21/PKC_(E) ratio increases in the cytoplasmic fraction of cancer cells.

In addition, the detection of the E2F1 and/or E2F4 proteins is advantageous. In fact, the LIV21 protein forms a complex with E2F4 which is capable of inhibiting the expression of the E2F1 gene in the nucleus, E2F1 gene expression being a sign of cell proliferation. Thus, a decrease in the association of LIV21 with the E2F4 protein is indicative of the presence of cancer cells.

Similarly, the presence of the E2F1 protein in the nucleus is indicative of the presence of cancer cells.

Consequently, the present invention concerns a method for the detection (in vitro or ex vivo) of cancer cells in a biological tissue sample (for example, breast, ovary, endometrium, bladder, melanoma, prostate, glioblastoma, etc.) from patients, this method comprising the detection of the product of expression of the LIV21 gene in the nucleus and/or the cytoplasm of the cells in the biological tissue sample from said patient, localization of said product of expression of the LIV21 gene in the cytoplasm being indicative of the presence of cancer cells, and localization of said product of expression of the LIV21 gene in the nucleus being indicative of the presence of noncancer cells.

Preferably, localization of said product of expression of the LIV21 gene in the cytoplasm is indicative of the presence of invasive and/or metastatic cancer cells.

Optionally, the method according to the present invention also comprises the detection of the product of expression of at least one gene selected from the group consisting of the protein kinase C epsilon (PKCE) gene, the E2F1 gene and the E2F4 gene. The method can in particular comprise the detection of the product of expression of two of these genes or of the three genes. Moreover, at least one of the ratios LIV21/PKCεLIV21/E2F4 and LIV21/E2F1 can be determined in the present method. This ratio can be determined in the cytoplasm and/or in the nucleus. Preferably, these ratios are determined in the nucleus. Preferably, these ratios are compared with those obtained in a normal cell.

The same is true of the detection of HDAC1, which has been shown to be involved in PML/SUMO/Rb/HDAC-1 complexes. More generally, the HDAC family plays a key role in the regulation of gene expression. When the HDACs are overexpressed, they bring about tumor suppressor gene silencing, hence the advantage of using HDAC inhibitors in therapy, combined with other inhibitors which regulate the metabolic cascade involving the protein complex which contains LIV21. The level of expression of each enzyme or polypeptide of the SUMO/Rb/HDAC complex or, for certain cell types, of the PML/SUMO/Rb/HDAC complex is an additional indictor of the proliferative state of the cell. Thus, in a specific embodiment, the method according to the present invention also comprises the detection of the product of expression of at least one gene selected from the group consisting of SUMO, Rb, HDAC and PML.

The methods according to the present invention also consist in using the detection of the LIV21 protein in combination with all the proliferation markers and transcription factors which play a role in the cancerization and neurodegeneration process. The method therefore also comprises the detection of the product of expression of at least one gene selected from the group consisting of RBP2, E2F4, E2F1, SUMO, HDAC1, cycE/cdk2, cdkl, CREB1, p300, Rb, PML, p107 and p130 of the pocket protein family. Thus, the invention lies in the fabrication and the use of diagnostic antibody arrays comprising LIV21-specific antibodies and antibodies for the various proteins of the LIV21-associated complex according to the phases of the cell cycle, that is, without restriction thereto, antibodies specific for RBP2, E2F4, E2F1, SUMO, HDAC1, cycE/cdk2, cdkl, CREB1, p300, Rb, PML, p107 and p130 of the pocket protein family (FIG. 1). In addition, the diagnostic arrays according to the present invention can comprise antibodies specific for NFkB, cdc2A, mdm2, p21, p53, p65, Ki67 and CAF1. Ki67 and CAF1 (Amoulzy; Institut Curie) are nuclear markers which signal the proliferative state of many cancers. The protein arrays will make it possible to study protein expression, protein interactions and post-translational modifications, more particularly phosphorylations and methylations of certain proteins, which signal a characteristic state of the diseased cell. The state of expression and of silencing of certain genes is different in diseased cells and in normal cells. Moreover, the protein interactions and the metabolism of the diseased cell are different from those of the normal cell.

The other aspect of the present invention is the use of the proteins mentioned above as markers for the invasiveness and the metastatic aggressiveness of cancer cells of the prostate, colon, bladder, melanoma, ovary, endometrium and cervix, and cancers in neurobiology, etc.

In one embodiment, the expression product of the genes is detected at the protein level. Preferably, the protein is detected using a specific antibody. For example, the protein can be detected by Western blotting analysis. In a preferred embodiment, it is detected by immunohistochemistry, immunocytochemistry or radiography, or by peroxidase labeling.

In one specific embodiment of the method comprising the detection of the expression product of the PKCE gene, a significant increase in PKCE is indicative of the presence of cancer cells. Moreover, the method can also comprise the determination of the LIV21/PKCE ratio in the nucleus and/or the cytoplasm. This ratio can be compared with that observed in a normal cell. An increase in the LIV21/PKCE ratio in the cytoplasmic fraction is indicative of cancer cells.

In another specific embodiment of the method comprising the detection of the expression product of the E2F4 gene, the method comprises the detection of the association of LIV21 with the E2F4 protein, a decrease in this association in the cell nucleus being indicative of the presence of cancer cells. Moreover, the method can also comprise the determination of the LIV21/E2F4 ratio in the nucleus and/or the cytoplasm. This ratio can be compared with that observed in a normal cell.

In an additional embodiment of the method comprising the detection of the expression product of the E2F1 gene, the presence of the E2F1 protein in the nucleus is indicative of the presence of cancer cells. Moreover, the method can also comprise the determination of the LIV21/E2F1 ratio in the nucleus and/or the cytoplasm. This ratio can be compared with that observed in a normal cell.

The method according to the present invention allows in particular the detection of metastasized cancer, therapeutic monitoring and/or recurrences following treatment.

A second aspect of the invention concerns the human LIV21 protein and also the fragments thereof. More particularly, the present invention concerns a purified or recombinant, isolated human LIV21 protein. It concerns in particular an isolated polypeptide having an apparent molecular weight of approximately 50-51 kD by Western blotting analysis and of approximately 60 kD when it is sumoylated and/or a polypeptide having an isoelectric point of 5.6 in its 50-51 kD form and/or a polypeptide characterized by one of the chromatograms of FIGS. 3-6 and/or a polypeptide comprising a peptide sequence selected from SEQ ID Nos 1-55, preferably from SEQ ID Nos 1-5, or a sequence having 70%, 80% or 90% identity to said sequences, and/or one of the peptide sequences obtained by MALDI (FIG. 7)and NanoLC-ESI-MS (FIG. 9). In a preferred embodiment, the polypeptide comprises the two peptide sequences SEQ ID Nos 1 and 2.

In an even more preferred embodiment, the polypeptide comprises a third peptide sequence SEQ ID No 3 and/or a fourth peptide sequence SEQ ID No 4 or a sequence having 70%, 80% or 90% identity to said sequences. Optionally, LIV21 also comprises a sequence selected from the sequences SEQ ID Nos 5-55 or a sequence having 70%, 80% or 90% identity to said sequences.

Preferably, the LIV21 protein comprises a leucine zipper motif, a basic domain characteristic of DNA binding domains, and a nuclearization sequence. Digestion of the LIV21 protein with trypsin gives more than 54 peptides corresponding to the monoisotopic peaks among all the peptides as specified, FIGS. 3-6; FIG. 7 or 9 (table); FIG. 8 (SDS PAGE gel). A third aspect of the invention concerns an antibody which binds specifically to a polypeptide according to the present invention. More particularly, the antibody can bind specifically to a polypeptide comprising a peptide sequence selected from SEQ ID Nos 1-55, preferably from SEQ ID Nos 1-5, or a sequence having 70%, 80% or 90% identity to said sequences. The present invention concerns in particular an anti-LIV21 serum produced by immunizing an animal or a human with a polypeptide according to the present invention, in particular a polypeptide comprising a peptide sequence selected from SEQ ID Nos 1-55, preferably from SEQ ID Nos 1-5, or a sequence having 70%, 80% or 90% identity to said sequences.

A fourth aspect of the invention concerns a kit for the detection of cancer cells in a biological sample from a patient, this kit comprising one or more elements selected from the group consisting of an antibody which binds specifically to human LIV21 according to the present invention and an anti-LIV21 serum according to the present invention. In a specific embodiment of the invention, the kit also comprises means for detecting the product of expression of a gene selected from the group consisting of the protein kinase C epsilon (PKCE) gene, the E2F1 gene and the E2F4 gene. Preferably, the detection means is an antibody specific for the protein concerned. In another preferred embodiment, the kit also comprises a means for detecting the product of expression of a gene selected from the group consisting of RBP2, SUMO, HDAC, PML, cycE/cdk2, cdkl, CREB1, p300, Rb, p107, p130, NFkB, cdc2A, mdm2, p21, p53, p65, Ki67 and CAF1. In a preferred embodiment, the kit comprises an antibody array comprising an LIV21-specific antibody. In a preferred embodiment, the array also comprises an antibody specific for a protein selected from PKC2, E2F1 and E2F4. In addition, it can comprise an antibody specific for a protein selected from RBP2, SUMO, HDAC1, cycE/cdk2, cdkl, CREB1, p300, Rb, PML, p107 and p130 of the pocket protein family. The array can also comprise an antibody specific for a protein selected from NFkB, cdc2A, mdm2, p21, p53, p65, Ki67 and CAF1.

The invention concerns the use of an antibody specific for human LIV21 for the diagnosis of cancer, and/or of one or more antibodies specific for a protein complex containing LIV21, for example antibodies specific for RBP2, E2F4, E2F1, SUMO, HDAC1, cycE/cdk2, cdkl, CREB1, p300, Rb, PML, p107 and p130 of the pocket protein family. Preferably, the diagnosis is performed ex vivo on samples from a patient.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1: antibody array.

FIG. 2: scheme of nuclear protein interactions and consequences on the study of therapeutics.

FIG. 3: LIV21 protein profile by mass spectrometry (Maldi) M (H+) for the one-dimensional gel band corresponding to the protein doublet migrating at 50 kD. The peptides derived from the digestion are solubilized in a solvent: acetonitrile/water (1/1) containing 0.1% of TFA (trifluoroacetic acid). A saturated solution of the alpha-cyano-4-hydroxycinnamic acid matrix is prepared in the same solvent. The same volume of the two solutions is taken and mixed together, and 1 microliter is deposited onto the Maldi plate for analysis. The spectrum was determined on a Voyager with Waters software. The calibration with respect to the autolysis and trypsin digestion peaks is not excellent and needs to be looked at again.

FIG. 4 is a zoomed-in profile of the chromatogram of the 49 kD band without smoothing.

FIGS. 5 and 5A are the second chromatogram corresponding to the one-dimensional 12% acrylamide gel band migrating at 49 kD and revealed with coomassie blue and the LIV21 antibody. The spectrum was determined on a Brucker apparatus.

FIGS. 6A-6F are the third chromatogram corresponding to the one- dimensional acrylamide gel band migrating at 53 kD and revealed with coomassie blue and the LIV21 antibody. The spectrum was also determined on a Brucker apparatus.

FIGS. 7A-7BB represent a table of the monoisotopic peaks with a value M H+. The masses are given with three numbers after the decimal point by the proteomic platforms since they estimate that this is the acquisition precision limit of MALDI TOF machines.

FIGS. 8A and 8B represent 2D SDS PAGE gel separating the twelve polypeptides bound by the LIV21 antibody.

FIGS. 9A-9V describe Nano LC-ESI MS characterized peptides, including the peptides of LIV21a and LIV21b,LIV21c,LIV21d,LIV21e. The table describes a NanoLC-ESI MS experiment. NanoLC makes it possible to separate the peptides derived from the trypsin hydrolysis of the protein. The eluted peptide fragments are ionized by electrospray and the ions formed are detected by mass spectrometry (Q-TOF analyzer). Each of these ions characterizes a peptide specific for the protein.

Legend illustrated by the first page describing the ion: molecular mass 523.25 daltons. Title: elution from 29.15 to 29.23 corresponds to the peptide eluted between 29.19 and 29.23 minutes. By ionization, this molecule gives the double-charge ion (charge=2+): MH2²⁺ of molecular mass m/z: 523.25 daltons, hence the mass of the molecule M: 1044.51. The peptide sequence of this ion is determined by MSMS. The corresponding MSMS spectrum is defined by the column of numbers between Begin ions and End ions, which corresponds to an amino acid sequence (each amino acid having a specific mass, except for leucine and isoleucine, which have the same molecular mass). The first column with a 4-decimal number (daughter ion: 86.1373) corresponds to the mass of the “daughter” ions. The second column (I: 45) corresponds to the intensity of these “daughter” ions.

FIGS. 9A-9V further describes the MSMS analyses giving a set of polypeptides that can be assigned to the LIV21 protein and its complex or contaminants according to the various observers of the various subcontracting proteomics platforms. Sequences common with Gallus gallus, the histatin variant HIS3-HUMAN, the HSP60 chaperonin, arginine deiminase, pseudomonas polyribonucleotide nucleotidyltransferase, dehydrogenase.

FIG. 10: describes the MALDI TOF analyses giving a set of polypeptide sequences (SEQ ID NOS: 3 and 4) that can be assigned to LIV21 and its complex and contaminants which are sometimes different according to the observers of the various subcontracting proteomics platforms. The Mascot search parameters are: trypsin enzyme, variable modifications: carbamethylation and oxidation of methionines, without molecular mass limit, without isoelectric point restriction. Type of mass: monoisotopic. Mass error (MS): according to the observer 50 ppm or 100 ppm. Non-cleavage with trypsin: 1 The masses captured are M (HI/real masses. For chromatogram 1, the cysteins are blocked with iodoacetamide. The possibility of digestion with Promega bovine trypsin may be incomplete with cleavage oversight.

Sequences common with Gallus gallus (gi 50732569), mouse syntaxin, the histatin-3-2 variant (P15516-00-01-00), ZN575-Human, G6 P translocase, the HSP60 chaperonin, arginine deiminase, ferredoxin-NADP(+) reductase, pseudomonas polyribonucleotidyl transferase, dehydrolipoamide dehydrogenase.

FIGS. 11A-11C represent alignments between the histatin-3-2 variant, PATF and Q7TCL4 (turnip mosaic virus) AAN08045.2. By Brucker MALDI TOF analysis. SEQ ID NOS: 57, 30, 7, 10, 39, 6, 35, 41, 34, 45, 40, 5, 36, 9, 46, 37, 31, 44, 38, 48 42, 33, 11, 49, and 47.

FIG. 12: alignments between Gallus gallus (gi 50732569) and

PATF and common polypeptide sequence derived from LIV21 by MALDI TOF analysis.

FIG. 13: example of a Maldi analysis interpretation diagram for histatin 3-2, giving sequence No. 5, selecting the masses: 2383.2610 (delta at 0.005); 2539.3290 (delta: -0.02); 2511.3740 (delta at 0.02). score: 78 and expect: 0.0046.

FIG. 14 is the morphology of MCF7 cells treated or not treated with TPA at 25 nM.

FIGS. 15A-15C represent an analysis by FACS; representation, for each phase of the cell cycle, of the percentage of cells as a function of treatment time: FIG. 15A. S phase, FIG. 15B. G2/M phase, FIG. 15C. GO/Gl phase. The scale along the x- axis is not proportional to the duration of treatment.

FIG. 16 is a Western blot comparing total extracts (ET) and nuclear extracts (EN) and showing the inhibition, with TPA, of the expression of LIV21 phosphorylation. FIG. 16A. as a function of the time of treatment with TPA at 25 nM; FIG. 16B. compared with LIV21 in protein extracts, at 12 h of treatment with TPA at 25 nM.

FIG. 17 is a study of the nuclear translocation of LIV21 by immunocytochemistry with an anti-LIV21 primary antibody (in green) in cultures treated or not treated with TPA at 25 nM. The nuclei are stained red with propidium iodide. The nuclei are predominantly stained yellow at 12 H until 24 H since the anti-LIV21 primary antibody (in green) is nuclear, whereas it is predominantly cytoplasmic at 72 H (red nuclei and green cytoplasms).

FIG. 18 shows the expression, as a function of time of treatment with TPA at 25 nM, of PKC8 and PKC proteins in total extracts. a-Tubulin expression serves as a control for the amount of total proteins loaded in the wells.

FIG. 19 shows the compared expression of PKC8 and of LIV21 by immunocytochemistry on MCF-7 cell cultures treated or not treated with TPA at 25 nM for 12 h, carried out with anti-LIV21 and anti-PKCε antibodies in green, and propidium iodide staining the DNA red. The LIV21 is translocated into the nucleus by specific inhibition of PKC8. The PKC8 is weakly expressed at 12 h in the presence of TPA. In fact, red nuclei and little green staining in the cytoplasms are observed. On the other hand, the expression of LIV21 is strong in the nuclei, which are stained yellow (merge) both with the anti-LIV21 antibody (green) and with the nucleus-specific propidium iodide.

FIG. 20 shows the effect of the PKC8-inhibiting peptide on the LIV21 expression profile by immunocytochemistry on cultures: control or treated with 1 μM of peptide, 2 μM of peptide, or 25 μM of TPA. The treatments last 12 hours. The cells are labeled with anti-LIV21 (in green), and with propidium iodide (in red). It is observed that 2 μM of peptide (image referred to as 2 pM) have the same effectiveness as “25 nM of TPA 12 H”: the nuclei (yellow) are predominantly labeled both with propidium iodide and with the anti-LIV21 antibody (in green) on these two images, whereas the control and the cells treated with only 1 μM of PKC-inhibiting peptide show red staining of the nuclei, reflecting the absence of nuclear translocation of LIV21 through its anti-LIV21 antibody (in green).

FIG. 21 shows the effect of the PKCE-inhibiting peptide on the LIV21 expression profile in cytoplasmic (C) and nuclear (N) cellular fractions, after treatment for 12 h with TPA (25 nM) or with peptide (2 pM).

FIG. 22 shows, by immunoprecipitation (IP), the coexistence between PML/SUMO and LIV21: nuclear yellow fluorescence (merge) corresponding to the colocalization of PML/SUMO and LIV21 is observed in the cell nuclei.

FIGS. 23 and 24 show, by immunocytochemistry, the coexistence between PML/SUMO and LIV21. The colabeling (by fluorescent immunolabeling) of LIV21 (green) and of SUMO-1 (red) in the nuclei of the cells treated or not treated with TPA for 24 h and 72 h show that, at 24 h, LIV21 is translocated into the nucleus where SUMO and PML coexist (merge: yellow nuclei), whereas, at 72 h, LIV21 (green) is cytoplasmic. The nuclear bodies containing the SUM01 protein are called PML bodies.

FIG. 25 shows that, using an array of 60 biopsies, including 50 of skin cancer and 9 of normal tissues and a control T; nuclear LIV21 expression is demonstrated in the biopsies of normal tissues and cytoplasmic LIV21 expression is demonstrated in the biopsies of metastatic cancers.

Image 43: poorly differentiated skin cancer T2NOMO, image 58: normal tissue derived from the same individual suffering from a poorly differentiated skin cancer (the nuclei of the cells are stained yellow), image 40: 10 cm metastatic carcinoma, and image 17: metastatic carcinoma of 3.5 cm. The cell nuclei are stained red.

FIG. 26 is, like FIG. 25, a second example of nuclear localization of LIV21 in the control and normal tissue (No. 52) (the cell nuclei are stained yellow), of the individual No. 7 suffering from a squamous cell carcinoma of the pharynx (moderately differentiated T4NOM0). In the images No. 7 of cancerous tissue, the cell nuclei are stained red.

FIG. 27 is a sample of advanced bladder cancer on cystectomy (grade III urethral carcinoma infiltrating the chorion and the musculosa) versus normal bladder tissue from the same patient with an internal control (PI): preimmune serum PI before the rabbit has been immunized against LIV21, red labeling of the nuclei with propidium iodide.

FIG. 28 is a sample.

DETAILED DESCRIPTION OF THE INVENTION

The invention relates to the identification of antigens in cell lysates by immunoprecipitation. The analysis of the physical interaction of various proteins associated with E2F4 and E2F1 has been studied by coimmunoprecipitation of protein complexes. This analysis has made it possible to demonstrate a novel marker which has a diagnostic and prognostic use for cancer.

A marker for PATF proliferation associated with the E2F family had been demonstrated (Crisanti) through the characterization of exons, without the gene having ever been cloned in humans nor a corresponding protein having ever been found in humans.

The discovery of this novel molecule LIV21 could have a diagnostic value for the following reasons. By carrying out a screening of the localization of LIV21 in about ten human tumors, the inventor has been able to observe that, in all proliferating tumor cells, this protein is cytoplasmic instead of nuclear. It is not therefore in the correct cellular compartment to be active on the arrest of cell multiplication.

It has thus been possible to observe the presence of LIV21 in mammals. The panel of LIV21 expression as a function of cell state (mitotic cycles, cell in the resting state, differentiation) has been studied on tissues originating from various mammals. Protein analyses on the various tissue samples have confirmed that the expression of this transcription factor appears to be associated with a progression toward a quiescent cell state (arrest of mitoses and entry into differentiation). LIV21 is present in actively proliferating tumor cell lines and its expression is essentially cytoplasmic. The same results are obtained on human mammary adenocarcinomas.

Thus, the present invention relates to a novel test for screening for anomalies of the reinduction of the cell cycle. This diagnostic test is based on the study of the mechanism of action of the novel gene, encoding a potential novel transcription factor called LIV21, which down-regulate proliferation. LIV21 is implicated in the arrest of cell proliferation. LIV21 is cytoplasmic when the cells proliferate, whereas it becomes nuclear when the cells become quiescent. The characterization of this factor suggests a new pathway for down-regulating cell proliferation, by virtue of its association with one of the members of the EF family: E2F4. The latter is known to down-regulate the cell cycle by association with the P130 protein or pocket protein of the RB family.

The localization observed for LIV21 in tumor cells (cytoplasmic localization) and in physiological cells (nuclear localization) suggests, in any event, that its function is disturbed when cell development becomes anarchical.

The characterization of this molecule and the study of the timing and the topology of its expression also indicate that the expression and the localization of this ubiquitous transcription factor are regulated as a function of cell state: greater expression and nuclear localization for cells which have exited mitotic cycles, weak expression and cytoplasmic localization for actively proliferating cells such as human tumor cells.

LIV21 appears to be a key molecule for stabilizing another transcription factor (E2F4) in the cell nucleus and thus for inducing an arrest of cell proliferation.

Furthermore, it has been shown that the localization of LIV21 in the cytoplasmic compartment is regulated by PKCE. In fact, when LIV21 is phosphorylated by PKCεLIV21 is located in the cytoplasmic compartment. Conversely, when the phosphorylation of LIV21 by PKCE is inhibited, LIV21 is located in the nuclear compartment.

LIV21

The present invention therefore concerns the LIV21 protein and derivatives and fragments thereof.

The LIV21 protein is a human protein of approximately 300 amino acids. However, depending on the alternative splicing that it undergoes, it exists as at least three forms of different sizes (FIG. 8). Moreover, it can be phosphorylated or sumoylated. It has an apparent molecular weight of between 50 kD and 51 kD in Western blotting analysis. This apparent molecular weight is 60 kD when LIV21 is sumoylated. In its 51 kD form, which may be phosphorylated or nonphosphorylated, its isoelectric point is 5.6 and its intensity is 13632. This protein has been characterized by mass spectrometry (Maldi) (Example 1; FIGS. 3-13 3). It gives more than 54 peptides following digestion with Promega trypsin (FIG. 7). The characteristics of the LIV21 protein are also described in FIGS. 3-13.

Several specific peptides of LIV21 have been characterized, and in particular the LIV21a peptide (SEQ ID No 1), the LIV21b peptide (SEQ ID No 2), the LIV21c peptide (SEQ ID No 3), the LIV21d peptide (SEQ ID No 4) and the LIV21e peptide (SEQ ID No 5). The longest sequence with the greatest sequence homology with PATF is the LIV21e peptide KFFVFALILALMLSMTGADSHAKR (SEQ ID No 5).

Other specific peptides of LIV21 are described below:

(SEQ ID NO: 6) RTLLLPAVSRQ (SEQ ID NO: 7) LGFMEEWDVGEIMLR (SEQ ID NO: 8) QIMAHFSDVAEAYIEK (SEQ ID NO: 9) FYAWMIEQAPFSSLAQEGK (SEQ ID NO: 10) NLYTEIVYTPISTPDGTLVK (SEQ ID NO: 11) GANNNLFGLDGNVGTTVENTER (SEQ ID NO: 12) KFQFGQSTVTLETGRI (SEQ ID NO: 13) KGFFPLSVHYQEKT (SEQ ID NO: 14) RTVRPLNIEVGVLPKT (SEQ ID NO: 15) RRSVQAMLPGADVFPYTIRV (SEQ ID NO: 16) KGITEEIMEIALGQALEARL (SEQ ID NO: 17) RAICEETKASIDIEDDGSIKI (SEQ ID NO: 18) KVTDILKEGQEVEVLVLDVDNRG (SEQ ID NO: 19) KMLTGVNVLADAVKA (SEQ ID NO: 20) RAAVEEGVVPGGGVALIRA (SEQ ID NO: 21) KVIIVAVDWDLSKE (SEQ ID NO: 22) KIFSPATVFFTSIEKH (SEQ ID NO: 23) KNVWILTGFQQGQEFPKF (SEQ ID NO: 24) RFNLFAGGSNKA (SEQ ID NO: 25) RAYSLLGTSERT (SEQ ID NO: 26) AMAANDTGGFVK (SEQ ID NO: 27) ASEEGIMVVER (SEQ ID NO: 28) FDVVVIGAGPGGYVAAIK (SEQ ID NO: 29) RPVTTDLLASDSGVTIDER (SEQ ID NO: 30) FYCGWDR (SEQ ID NO: 31) DVAQEEGK (SEQ ID NO: 32) SGIPSELR (SEQ ID NO: 33) EAHIQMK (SEQ ID NO: 34) EGIWIPK (SEQ ID NO: 35) YTFDSR (SEQ ID NO: 36) LTHEIR (SEQ ID NO: 37) LYLDK (SEQ ID NO: 38) YGLQR (SEQ ID NO: 39) DSIIR (SEQ ID NO: 40) LEAICAAMIESWGYDK (SEQ ID NO: 41) GDLWFMSHQGHK (SEQ ID NO: 42) YAFDFYEMTSR (SEQ ID NO: 43) EVNAGTSGTFSVPR (SEQ ID NO: 44) NQDRPYMPR (SEQ ID NO: 45) IVSILEWDR (SEQ ID NO: 46) APYIAETALR (SEQ ID NO: 47) NMHNLLGVK (SEQ ID NO; 48) NLTDMSLAR (SEQ ID NO: 49) HTTEDVNR (SEQ ID NO: 50) KFFVFAL (SEQ ID NO: 51) FVFALILALMLSMCG (SEQ ID NO: 52) TLQIFNIEMKSK (SEQ ID NO: 53) KDPELWAHVLEE1NTSR (SEQ ID NO: 54) KSWEVYQGVCQK (SEQ ID NO: 55) HTSLVGCQVIHYR

For the purposes of the invention, a preferred LIV21 protein comprises at least one sequence chosen from SEQ ID Nos 1-55 or a sequence having 70%, 80% or preferably 90% homology with said sequence.

The LIV21 protein comprises a leucine zipper motif, a basic domains characteristic of DNA binding domains, and a nuclearization sequence.

The present invention concerns a purified or recombinant, isolated human polypeptide having a sequence comprising the sequence SEQ ID No 1 and/or SEQ ID No 2. Preferably, the polypeptide comprises the sequences SEQ ID Nos 1 and 2. In a preferred embodiment, the polypeptide comprises (in addition) a sequence selected from SEQ ID Nos 3-55, preferably from SEQ ID Nos 3-5, or a sequence having 70%, 80% or 90% identity to said sequences. In a specific embodiment, it comprises a sequence selected from one of the peptide sequences obtained by MALDI (FIG. 7) and NanoLC-ESI-MS (FIG. 9). The invention also concerns the two peptides LIV21a (SEQ ID No 1) and LIV21b (SEQ ID No 2). The invention also concerns a peptide having a sequence selected from SEQ ID Nos 3-55, preferably from SEQ ID Nos 3-5, or a sequence having 70%, 80% or 90% identity to said sequences. It also concerns peptides comprising at least 10 consecutive amino acids of human LIV21, preferably at least 20, 30 or 50 consecutive amino acids of LIV21.

The invention also concerns LIV21 derivatives of interest which are, for example, fusion proteins in which LIV21 is fused to labeled proteins such as GFP. Moreover, the LIV21 protein can be labeled by any means known to those skilled in the art.

The present invention also concerns an antibody which binds specifically to a polypeptide according to the present 0invention, preferably human LIV21, or a fragment or a derivative thereof. In a specific embodiment, the antibody binds specifically to an LIV21a or LIV21b peptide. In a preferred embodiment, the antibody binds specifically to a polypeptide comprising a sequence selected from SEQ ID Nos 1-55, preferably from SEQ ID Nos 1-5, or a sequence having 70%, 80% or 90% identity to said sequences.

The antibodies may be polyclonal or monoclonal. They may be antibody fragments and derivatives having substantially the same antigenic specificity, in particular antibody fragments (for example, Fab, Fab'2, CDRs), humanized antibodies, polyfunctional antibodies, single-chain antibodies (ScFv), etc.

The antibodies of the invention can be produced using conventional methods, including the immunization of an animal and the recovery of its serum (polyclonal) or of spleen cells (so as to produce hybridomas by fusion with appropriate cell lines).

Said antibodies can be obtained directly from human serum or from serum of animals immunized with the proteins or the peptides according to the present invention. Methods for producing polyclonal antibodies from varied animal species including rodents (mice, rats, etc.), primates, horses, pigs, sheep, rabbits, poultry, etc., are described, for example, in Vaitukaitis et al. (Vaitukaitis, Robbins et al. 1971). The antigen is combined with an adjuvant (for example, Freund's adjuvant) and administered to an animal, typically by subcutaneous injection. Repeated injections can be carried out. Blood samples (immune serum) are collected and the immunoglobulins are separated.

The present invention concerns an anti-LIV21 serum produced by immunizing an animal with a polypeptide according to the present invention. In a specific embodiment, the animal was immunized with the LIV21a and/or LIV21b peptide. In a preferred embodiment, the animal is immunized with these two peptides. The present invention also concerns an anti-LIV21 serum produced by immunizing an animal or a human with a polypeptide according to the present invention, in particular a polypeptide comprising a peptide sequence selected from SEQ ID Nos 1-55, preferably from SEQ ID Nos 1-5, or a sequence having 70%, 80% or 90% identity to said sequences. For example, the peptides can be coupled to a carrier protein such as hemocyanin, and then injected into an animal, for example a rabbit, for immunization. Polyclonal antibodies were obtained using these two peptides by having immunized two rabbits and having bled one rabbit so as to have a preimmune serum.

Methods for producing monoclonal antibodies from various animal species can be found, for example, in Harlow et al. (Harlow 1988) or in Kohler et al. (Kohler and Milstein 1975) These methods include the immunization of an animal with an antigen, followed by the recovery of the spleen cells, which are subsequently fused with immortalized cells, such as myeloma cells. The resulting hybridomas produce monoclonal antibodies and can be selected by limiting dilution so as to isolate the individual clones. The antibodies can also be produced by selection from combinatorial libraries of immunoglobulins, such as those disclosed, for example, in Ward et al. (Ward, Gussow et al. 1989).

The invention also includes the use of the antibodies according to the invention for the detection and/or the purification of the human LIV21 protein. In particular, the LIV21-specific antibodies can be used for the detection of these proteins in a biological sample. They thus constitute a means of immunocytochemical or immunohistochemical analysis of LIV21 expression on tissue sections. Generally for such analyses, the antibodies used are labeled in order to be detectable. As an alternative, the antibodies can be indirectly labeled.

In a preferred embodiment, the antibodies are labeled. The labels include radiolabels, enzymes, fluorescent, luminescent or chemical labels, magnetic particles, gold labeling, biotin/avidin labeling, peroxidase labeling, etc.

The invention also includes a method for detecting the LIV21 protein in a biological sample, comprising a step of suitable treatment of the cells by any appropriate means which makes it possible to render the intracellular medium accessible, a step of bringing said intracellular medium thus obtained into contact with an antibody specific for the human LIV21 protein and a step of demonstrating the LIV21-antibody complex formed, by any appropriate means. In specific embodiments, the cytoplasmic and/or nuclear extracts are prepared, and these extracts are brought into contact with the antibody specific for the human LIV21 protein.

Diagnosis

The present invention teaches the development of the diagnostic test which also makes it possible to monitor the evolution of a cell proliferation. In particular, the present invention makes it possible to monitor the evolution of a cell proliferation on fresh cells or tissues, on frozen cells or tissues and on tissues processed, inter alia, with paraffin. The applications may be the diagnosis of cancer and also the monitoring of the evolution of a cell proliferation. Preferably, the cancer is selected from breast cancer, bladder cancer, ovarian cancer, lung cancer, skin cancer, prostate cancer, colon cancer, liver cancer, a sarcoma, a leukemia and glioblastoma, without being limited thereto.

Four of these properties can be used: its passage from the cytoplasmic cellular compartment to the nuclear compartment, the property of associating with the E2F4 transcription factor in order to forma complex which inhibits the expression of the E2F1 factor, and the ability of LIV21 to translocate in the nucleus through specific inhibition of PKC E, the sumoylation of LIV21 when the latter is nuclear and integrated into PML bodies and its interaction with HDAC.

The predominantly cytoplasmic state of this protein in cases of cancer, compared with its nuclear location in normal cells, is a geographical and structural difference which makes it possible, without the need for a fluorescent label, to differentiate spectral profiles of the functional pattern of cancerous tissue versus normal tissue, and thus to make the diagnosis.

These results show that the cytoplasmic localization of LIV21 is an indicator of the aggressiveness and of the metastatic potential of the cancer. The detection of the LIV21 expression indicates the presence of cancer cells, more particularly of invasive, aggressive and/or metastatic cancer cells. These results also show that the nuclear localization of LIV21 is an indicator of normal quiescent cells or of well-differentiated tissues.

The invention concerns, moreover, methods for the diagnosis or prognosis of cancer which implement the detection of the cytoplasmic localization of a transcription factor located in the nucleus in normal cells.

The present invention concerns a method for the detection of cancer cells in a biological sample from a patient, comprising the detection of the product of expression of the LIV21 gene in the nucleus and/or the cytoplasm of the cells in the biological sample from said patient, localization of said product of expression of the LIV21 gene in the cytoplasm being indicative of the presence of cancer cells and localization of said product of expression of the LIV21 gene in the nucleus being indicative of the presence of noncancer cells. Preferably, localization of said product of expression of the LIV21 gene in the cytoplasm is indicative of the presence of invasive and/or metastatic cancer cells. The method preferably comprises a prior step of suitable treatment of the cells contained in the sample by any appropriate means which makes it possible to render the intracellular medium accessible. The method optionally comprises a step of comparison with a biological sample which does not contain cancer cells.

Optionally, the method according to the invention also comprises the detection of the product of expression of at least one gene selected from the group consisting of the protein kinase C epsilon (PKCE) gene, the E2F1 gene and the E2F4 gene. The method can in particular comprise the detection of the product of expression of two of these genes or of the three genes. Moreover, at least one of the ratios LIV21/PKCε, LIV21/E2F4 and LIV21/E2F1 can be determined in the present method. This ratio can be determined in the cytoplasm and/or in the nucleus. Preferably, these ratios are determined in the nucleus.

Preferably, these ratios are compared with those obtained in a normal cell.

The method can also comprise the detection of the product of expression of at least one gene selected from the group consisting of RBP2, E2F4, E2F1, SUMO, HDAC1, cycE/cdk2, cdkl, CREB1, p300, Rb, PML, p107 and p130 of the pocket protein family. It can also comprise the detection of the product of expression of at least one gene selected from the group consisting of NFkB, cdc2A, mdm2, p21, p53, p65, Ki67 and CAF1.

The method can comprise the detection of an interaction between some of these proteins and/or the detection of a posttranslational modification of one of these proteins.

In a preferred embodiment, the expression product of the genes is detected at the protein level. Preferably, the protein is detected using a specific antibody. Thus, the method comprises a step of bringing the cells of the biological sample into contact with an anti-human LIV21 antibody. The antibodies may be monoclonal or polyclonal. The anti-LIV21 antibody can, for example, be an anti-LIV21 serum.

When the product of expression of one of the genes PKCε, E2F1 and E2F4 must be detected, the method can use antibodies specific for the PKCε, E2F1 and E2F4 proteins, respectively. Polyclonal and monoclonal antibodies directed against PKCεE2F1 and E2F4 are commercially available. By way of example, mention may be made of, for PKCεa rabbit polyclonal antibody (Santa Cruz Technology, sc-214), for E2F1, a rabbit polyclonal antibody (Santa Cruz Technology, sc-860), and for E2F4, a rabbit polyclonal antibody (Santa Cruz Technology, sc-866). Preferably, the antibodies are labeled, directly or by means of a secondary antibody. The antibody labeling techniques are well known to those skilled in the art.

In a specific embodiment, the protein can be detected by Western blotting analysis. The Western blotting analysis can be carried out on nuclear and/or cytoplasmic extracts of the cells contained in the sample from the patient. Briefly, the proteins are migrated in a gel and then blotted onto a membrane. This membrane is then incubated in the presence of the antibodies and the binding of the antibodies is optionally revealed using labeled secondary antibodies.

In another embodiment, the protein is detected by immunohistochemistry, immunocytochemistry or immunoradiography. These techniques are well known to those skilled in the art. The immunocytochemical analysis can be carried out on whole cells originating from the sample or which are derived therefrom, for example by cell culture. It can also be carried out on isolated nuclei. The immunohistochemical analysis can be carried out on mammary tissue sections.

By way of illustration, an immunocytochemical analysis can include the following steps. However, it is understood that other preparatory methods can be carried out. Cells originating from the biological sample are cultured, preferably on slides (Lab Tek, Nunc, Germany), and then washed with buffer and fixed with paraformaldehyde (for example, 4%). A saturation step is preferably carried out by incubating the cells with buffer S (PBS-0.1% Triton X100 10% FCS). The cells are then incubated with a primary antibody and are then washed and incubated with a fluorescent secondary antibody, if necessary. The nuclei can be labeled with propidium iodide (Sigma). The slides are mounted in moviol for observation by fluorescence microscopy. Moreover, isolated nuclei sampled during a nuclear extraction can be fixed with paraformaldehyde (for example, 4%). The suspensions of nuclei are deposited between a slide and cover slip and the observation is carried out by fluorescence microscopy and by confocal microscopy. The primary antibodies are, for example, rabbit antibodies and the secondary antibodies are labeled antibodies directed against rabbit IgGs.

The present invention also concerns the use of a protein array for detecting the expression of one or more of these proteins, and/or an interaction between two or more of these proteins, and/or the posttranslational modification of one or more of these proteins.

In a preferred embodiment, the detection of the product of expression of one or more genes or of the interaction between several proteins is carried out by means of a protein array.

Thus, a polypeptide according to the present invention, in particular LIV21 or a fragment thereof, or an antibody specific thereto, or a fragment or a derivative thereof which conserves the binding specificity, can advantageously be immobilized on a support, preferably a protein array. Such a protein array is included in the invention. This array can also contain at least one polypeptide selected from the group consisting of protein kinase C epsilon (PKCE), RBP2, E2F4, E2F1, SUMO, HDAC1, cycE/cdk2, cdkl, CREB1, p300, Rb, PML, p107 and p130 of the pocket protein family or at least one antibody specific for one of these polypeptides, or a fragment or a derivative thereof which conserves the binding specificity. The array can also comprise other polypeptides well known to those skilled in the art to be advantageous for the detection and/or the prognosis of a cancer, or antibodies specific for said polypeptides. These polypeptides can, for example, be selected from the following list: NFkB, cdc2A, mdm2, p21, p53, p65, Ki67 and CAF1.

The protein arrays according to the present invention can be prepared according to the techniques well known to those skilled in the art. In practice, it is possible to synthesize the attached polypeptides directly on the protein array, or it is possible to perform an ex situ synthesis followed by a step of attachment of the synthesized polypeptide to said array. Moreover, the polypeptides or antibodies to be attached can be purified from a cell. The supports include smooth supports (for example, metal, glass, plastic, silicon, and ceramic surfaces) and also texturized and porous materials. Such supports also include, but are not limited to, gels, rubbers, polymers and other flexible materials. The supports do not need to be flat.

The proteins or antibodies of the array can be attached directly to the support or can be attached by means of a spacer or a linker.

In a specific embodiment, an LIV21-specific antibody or a fragment or derivative thereof which conserves the binding specificity is immobilized on the solid support. Thus, this array provides a practical means for measuring the LIV21 expression product. Preferably, the array comprises at least one antibody specific for a polypeptide selected from the group consisting of PKCεRBP2, E2F4, E2F1, SUMO, HDAC1, cycE/cdk2, cdkl, CREB1, p300, Rb, PML, p107 and p130 of the pocket protein family, preferably PKCεE2F1 and E2F4. The array also comprises at least one antibody specific for a polypeptide known to those skilled in the art to be advantageous for the detection and/or the prognosis of a cancer, for example NFkB, cdc2A, mdm2, p21, p53, p65, Ki67 and CAF1. The array can comprise an antibody or a fragment or derivative thereof which has the same specificity. The protein arrays according to the invention are also extremely useful for experiments in proteomics, which studies the interactions between the various proteins. In a simplified manner, peptides representative of the various proteins are attached to a support. Said support is then brought into contact with labeled proteins and, after an optional rinsing step, interactions between said labeled proteins and the peptides attached to the protein array are detected.

“Protein array” is intended to denote a support to which are attached polypeptides or antibodies, it being possible for each of them to be pinpointed by its geographical location. These arrays differ mainly in terms of their size, the material of the support and, optionally, the number of polypeptides which are attached thereto.

The protein arrays can also be useful for the screening of test compounds.

The present invention also relates to a method for the detection of cancer cells in a biological sample from a patient, comprising the detection of the product of expression of the LIV21 gene in the nucleus and/or the cytoplasm of the cells in a sample of cells in the biological sample from said patient, which method is characterized in that it comprises at least: (a) bringing said biological sample into contact with a protein array as defined above, and (b) revealing, by any appropriate means, antigen-antibody complexes formed in (a), for example by EIA, ELISA or RIA or by immunofluorescence. Other detection methods are described in detail in the following document: US2004152212.

Methods applicable for the synthesis of protein arrays are described, for example, in the following patents: W02004/063719, W02005/016515, US2005019828, W003018773, US2002187464, U.S. Pat. Nos. 5,143,854, 5,242,974, 5,252,743, 5,324,633, 5,384,261, U52006035387, U52005100947, US2005233473, W00198458, W00172458, W00004382, W00004389, W09015070, W09210092, W09310161, W09512808 and W09601836, the content of these patents being incorporated into the present application by way of reference. For example, these protein arrays can be fabricated according to conventional methods described (Lubman David M, QIAO TIECHENG Alex, Mathew ABY J etc.) or novel tools for the automation of hybridization and of reading, US2004152212 and Yu Xinglong US 2005019828 and novel supports which attach polypeptides, Claus Peter Klages et al. (example FIG. 2).

The biological samples originate from a patient potentially suffering from cancer or for whom it has been established that said patient is suffering from cancer. “Biological sample” is intended in particular to mean a sample of the biological fluid, living tissue, tissue fragment, mucosity, organ or organ fragment type, or any culture supernatant obtained by means of taking a sample. The method according to the present invention can comprise a step of taking a biological sample from the patient. The detection step can be carried out directly on a tissue section of the sample, or on a culture of cells originating from the sample, or on total cell extracts, nuclear extracts and/or cytoplasmic extracts. The sample from the patient can come from a puncture, a biopsy, ground cellular material, a bronchial aspiration, a blood sample or a urine sample.

In a specific embodiment of the method comprising the detection of the product of expression of the PKCE gene, a significant increase in PKCE is indicative of the presence of cancer cells. More specifically, the amount of PKCE in normal cells is compared with the amount of PKCE in the cells of the sample, and the significant increase is determined by means of this comparison. The method according to the present invention can optionally comprise the measurement of the LIV21/PKCE content.

This LIV21/PKCε ratio increases in the cytoplasmic fraction of cancer cells compared with normal cells.

In another specific embodiment of the method comprising the detection of the product of expression of the E2F4 gene, the method comprises the detection of the association of LIV21 with the E2F4 protein, and a decrease in this association is indicative of the presence of cancer cells. The detection of the association of LIV21 with the E2F4 protein can be carried out by concurrent detection of LIV21 and of E2F4 and/or by the concurrent measurement of HDAC1. The method according to the present invention can optionally comprise the measurement of the E2F4/LIV21 content. This E2F4/LIV21 ratio decreases in the nucleus of cancer cells compared with normal cells.

In an additional embodiment of the method comprising the detection of the product of expression of the E2F1 gene, the presence of the E2F1 protein in the nucleus is indicative of the presence of cancer cells. The method according to the present invention can optionally comprise the measurement of the E2F1/LIV21 content. This E2F1/LIV21 ratio increases in the nuclear fraction of cancer cells compared with normal cells.

The method according to the present invention allows in particular the detection of metastasized cancer, therapeutic monitoring and/or recurrences following treatment and makes it possible to determine the degree of invasiveness of a cancer. The specificity of the detection can be related to the crossing over of information obtained through the existence and the topography of LIV21 by all imaging and spectroscopy means and obtained by combination with other known cancerological indicators via protein arrays or microarrays. Thus, the detection based on LIV21 can be combined with the detection of other cancer markers, in particular breast cancer markers, known to those skilled in the art.

In fact, the present invention concerns a method for the therapeutic monitoring of an anticancer treatment in a patient suffering from cancer, comprising the administration of the anticancer treatment to said patient and the detection of cancer cells in a biological sample from the patient, according to the method of the present invention. A decrease in cancer cells will be indicative of the effectiveness of the treatment. The detection of cancer cells in a biological sample from the patient, according to the method of the present invention, can be carried out once or several times over the course of the anticancer treatment or after the anticancer treatment. Preferably, the biological sample originates from the tissue affected by the cancer treated.

Moreover, the present invention also concerns a method for the detection of recurrences subsequent to an anticancer treatment of a cancer in a patient, comprising the detection of cancer cells in a biological sample from the patient, according to the method of the present invention. The detection of cancer cells in a biological sample from the patient, according to the method of the present invention, can be carried out once or several times after the anticancer treatment. The detection of cancer cells is indicative of recurrences. Preferably, the biological sample originates from the tissue affected by the cancer treated.

The present invention also describes a kit for carrying out a method according to the invention. More particularly, the invention concerns a kit for the detection of cancer cells in a biological sample from a patient, comprising one or more elements selected from the group consisting of an antibody which binds specifically to human LIV21 according to the present invention and an anti-LIV21 serum according to the present invention. In a preferred embodiment, the kit comprises antibodies which bind specifically to human LIV21.

The kit according to the present invention can comprise reagents for the detection of an LIV21-antibody complex produced during an immunoreaction. Optionally, the kit according to the present invention also comprises means for detecting the product of expression of at least one gene elected from the group consisting of the protein kinase C epsilon (PKCε) gene, the E2F1 gene and the E2F4 gene. This detection means can be antibodies specific for the protein.

The present invention also concerns a diagnostic composition comprising one or more elements selected from the group consisting of an antibody according to the present invention and a serum according to the present invention.

Anticancer Therapy

In the context of an anticancer therapy, it is possible to envision increasing the amount of LIV21 present in the nucleus. For this, the nuclear localization of LIV21 could be promoted, for example by decreasing the activity of PKCε in the cancer cells and by using HDAC inhibitors.

In another specific embodiment of anticancer therapy, it is possible to envision decreasing the activity of PKCε in the cancer cells. This decrease in activity can be produced by decreasing the activity of the PKCE protein or by decreasing its expression. A decrease in the activity of the PKCE protein can be obtained by administering PKCE-protein inhibitors to the cancer cells. The PKCε-protein inhibitors are well known to those skilled in the art. A decrease in the expression of the PKCε protein can be obtained by using antisenses or siRNA specific for the PKCE gene. Kits are commercially available.

Moreover, the techniques concerning inhibition by means of antisense or siRNA are well known to those skilled in the art (Arya R 2004, Lee W 2004, Sen A 2004, Platet N 1998, Hughes 25 1987).

The present invention therefore concerns a pharmaceutical composition comprising a PKCE-protein inhibitor. It also concerns the use of a pharmaceutical composition comprising a PKCE-protein inhibitor as a medicament, in particular for the preparation of a medicament for use in treating cancer. Finally, it concerns a method for treating cancer in a patient, comprising the administration to the cancer cells of a PKCε protein inhibitor, the PKCε-protein inhibitor making it possible to reduce or abolish the cancerous phenotype of the treated cells. In a first embodiment, the PKCε-protein inhibitor decreases the activity of the PKCE protein. In a second embodiment, the PKCE-protein inhibitor decreases the expression of the PKCε protein. Preferably, cancer is selected from breast cancer, bladder cancer, ovarian cancer, lung cancer, skin cancer, prostate cancer, colon cancer, liver cancer, a sarcoma, a leukemia and glioblastoma, without being limited thereto.

In the context of a therapy for a neurodegenerative disease, it is possible to envision decreasing the amount of LIV21 present in the nucleus. The cells affected by the neurodegenerative disease are generally neurons, motor neurons, etc. In a preferred embodiment, the neurodegenerative disease is chosen from Alzheimer's disease, Huntington's disease, Parkinson's disease and amyotrophie lateral sclerosis (ALS). For 20 this, the nuclear localization of LIV21 could also be hindered, for example by increasing the activity of PKCE in the cells affected by the neurodegenerative disease. This increase in activity can be produced by increasing the activity of the PKCE protein or by increasing its expression. An increase in the 25 activity of the PKCE protein can be obtained by administering PKCE -protein activators to the cells affected by the neurodegenerative disease. The PKCE-protein activators are well known to those skilled in the art (Toma 0 (2004), Activation of PKCE by DAG, 30 AGPI: oleic acid, linoleic acid, arachidonic acid, etc. Activation and proteolysis of PKCE in gonadotropic cells: Communication 2004 by Macciano H, Junoy B, Mas J L, Drouva S V, UMR6544 Marseille). An increase in the expression of the PKCE protein can be obtained by using expression vectors encoding the PKCE protein and which make it possible to overexpress it in the cells affected by the neurodegenerative disease.

Thus, the present invention concerns a pharmaceutical composition comprising a PKCE-protein activator or an expression vector encoding the PKCE protein. It also concerns the use of a PKCE -protein activator or of an expression vector encoding the PKCε protein, for the preparation of a medicament for use in the treatment of a neurodegenerative disease.

Screening Method

The invention concerns methods for the selection, identification, characterization or optimization of active compounds which decrease cell proliferation, based on the measurement of the nuclear versus cytoplasmic localization of LIV21, or of the binding of the LIV21 protein to the E2F4 protein.

In a first embodiment, the selection, the identification, the characterization or the optimization of active compounds of therapeutic interest comprises bringing a candidate compound into contact with a cell and determining the nuclear versus cytoplasmic localization of the LIV21 expression product. An increase in the nuclear localization of LIV21 indicates that the candidate compound is active in terms of decreasing or abolishing cell proliferation. A decrease in the nuclear localization of LIV21 indicates that the candidate compound is active in terms of treating or preventing a neurodegenerative disease.

In a second embodiment, the selection, the identification, the characterization or the optimization of active compounds of therapeutic interest comprises bringing a candidate compound into contact with a cell and determining the level of expression of the gene encoding the PKCE protein. A decrease in the expression of PKCE indicates that the candidate compound is active in terms of decreasing or abolishing cell proliferation. An increase in the expression of PKCE indicates that the candidate compound is active in terms of treating or preventing a neurodegenerative disease.

In a third embodiment, the selection, the identification, the characterization or the optimization of active compounds of therapeutic interest comprises bringing a candidate compound into contact with a cell and determining the level of LIV21/E2F4 complex. An increase in the level of LIV21/E2F4 complex indicates that the candidate compound is active in terms of decreasing or abolishing cell proliferation. A decrease in the level of LIV21/E2F4 complex indicates that the candidate compound is active in terms of treating or preventing a neurodegenerative disease.

In a fourth embodiment, the selection, the identification, the characterization or the optimization of active compounds of therapeutic interest comprises bringing a candidate compound into contact with a cell and determining the level of expression of the gene encoding the E2F1 protein. A decrease in the expression of E2F1 indicates that the candidate compound is active in terms of decreasing or abolishing cell proliferation. An increase in the expression of E2F1 indicates that the candidate compound is active in terms of treating or preventing a neurodegenerative disease.

The invention also relates to a method of screening for a compound capable of interacting in vitro, directly or indirectly, with LIV21, characterized in that: in a first step, the candidate compound and LIV21 are brought into contact and, in a second step, the complex formed between said candidate compound and LIV21 is detected by any appropriate means.

The present invention also relates to a method of screening for a compound capable of modulating (activating or inhibiting) the activity of the LIV21 protein, characterized in that: in a first step, cells of a biological sample expressing the LIV21 protein are brought into contact with a candidate compound, in a second step, the effect of said candidate compound on the activity of said LIV21 protein is measured by any appropriate means, and in a third step, candidate compounds capable of modulating said activity are selected. The activity of LIV21 can, for example, be estimated by means of evaluating the ability of the cell to divide, by measuring the expression of the E2F1 gene or by the cytoplasmic and/or nuclear localization of LIV21.

The candidate compound can be a protein, a peptide, a nucleic acid (DNA or RNA), a lipid, or an organic or inorganic compound.

In particular, the candidate compound could be an antibody, an antisense, a ribozyme or an siRNA.

Other advantages and characteristics of the invention will appear in the examples and the figures which follow, and which are given in a nonlimiting manner.

EXAMPLES Example 1

The inventor performed mass spectrometry (MALDI) for the LIV21 protein based on a one-dimensional acrylamide gel. The LIV21 protein was digested with trypsin. The peptides derived from the digestion are solubilized in a solvent: acetonitrile/water (1/1) containing 0.1% of TFA (trifluoroacetic acid). A saturated solution of the alpha-cyano-4-hydroxycinnamic matrix was prepared in the same solvent. The same volume of the two solutions was taken and mixed together and 1 μl was deposited onto the MALDI plate for analysis. The mass spectrometry showed that the LIV21 protein digested with trypsin reveals 54 peptides (cf. FIGS. 3-4). The LIV21 protein was characterized by a molecular weight of 50 kD, revealed by Western blotting. Since the first MALDI results were not probative, the inventor produced a two-dimensional SDS PAGE gel (FIG. 8). More than ten proteins were revealed by silver nitrate staining, but the very small amount of material did not make it possible to test samples derived from this gel by MALDI or MSMS.

When it changes cell compartment and when it is sumoylated, the LIV21 protein has a molecular weight of approximately 60 kD. When it is phosphorylated in the cytoplasm, it exhibits two forms which differ by a few kilobases. A doublet is then observed.

The inventor performed a third MALDI analysis, which gave interesting results, especially with regard to the 49 kD gel band, on Gallus gallus and a histatin variant (figure, the inventor then examined the sequence alignments, which made it possible to confirm homologies between Gallus gallus, PATF, Q7TCL4 and the polypeptides of histatin and of Gallus gallus (FIGS. 10 to 13)).

Only two peptides characterize in common PATF and LIV21:—The LIV21a peptide is located between a site of interaction with the Rb/p107/p130 protein (ITCCE) and a site of sumoylation by SUM01.

The sequence of this peptide is the following:

Peptide LIV21a RVYGPLTNPKPQ SEQ ID No 1

-   -   The LIV21b peptide is located between a sumoylation site (PKPG)         and a phospholipase C site (YVKI) followed by (KKKRK) NLS. The         sequence of this peptide is the following:

Peptide LIV21b CYRSILHTKV SEQ ID No 2

-   -   The LIV21c peptide SYMSMFLLLMAISCVLAK SEQ ID No 3     -   The LIV21d peptide PLMIIHHLDDCPHSQALK SEQ ID No 4.

Other peptides are provided in the sequences SEQ ID Nos 5-55.

Example 2 Study of the Nuclear Translocation of LIV21 in MCF-7 Cells

The study of the subcellular distribution of LIV21 in different tumor lines of various origins showed an exclusively cytoplasmic localization of this protein. The mechanism(s) by which LIV21 could be translocated into the nucleus in order to act on the cell cycle was (were) shown.

The presence of putative sites for phosphorylation by protein kinases C (PKCE), based on the possible homology that PATF is thought to have with the LIV21 sequence, directed the inventor's study toward a possible involvement of these proteins with respect toits nuclear translocation. The inventor therefore chose to study the MCF-7 line treated with TPA, which is known to modulate PKCε.

In parallel to this work, the inventor also studied the expression and the localization of cell cycle proteins implicated in the signaling pathway in which LIV21 could act.

The MCF-7 Cell Line

The MCF-7 line is a nonclonal human line of breast adenocarcinoma cells. During their differentiation induced by exogenous factors, these cells develop a hypertrophy, membrane protrusions and a tendency to dissociate from one another. They acquire a secretory phenotype which is characterized by the appearance of numerous granules and of secretory canaliculi.

In vivo, these cells are relatively nonmetastatic and this low invasiveness is thought to be due to a low constitutive activity of the protein kinases C (PKCE) and to a relatively 25 low level of expression of protein kinase C alpha.

This line is used in many studies on proliferation, differentiation and apoptosis. These studies use appropriate drugs, such as TNF for the induction of apoptosis, or TPA (12-0-tetradecanoyl phorbol-13-SUMOate) for the induction of differentiation and therefore for the study of departure from the cell cycle.

The Effect of TPA on the MCF-7 Line

TPA is a known activator of PKCE. It activates the growth of normal breast cells, does not modify the proliferation of the cells of benign tumors from this same tissue, but drastically inhibits the proliferation of the cells of human mammary tumor lines such as the MCF-7 line. It reduces the cell_growth of this line by positively controlling the c-erb-2 receptor and negatively controlling the retinoic acid receptor a, which are both expressed in particularly large amount in these cells. TPA greatly and rapidly inhibits the expression and the function of estrogen receptors (ERs) and it induces the time- and dose-dependent translocation of protein kinases C (PKCE) from the cytosol to the membranes. Furthermore, TPA increases the migratory capacity of MCF-7 cells in vitro and a short period of treatment of these cells with TPA induces cellular expansion and microtubule organization characteristic of their differentiation.

Expression of LIV21 in MCF-7 Cells

Firstly, the inventor verified the expression of LIV21 in these cells at the protein level.

The inventor tackled the study of the expression of the LIV21 protein through the Western blotting technique, with an anti-LIV21 antibody, in MCF-7 cells compared with mammary tissues. The anti-LIV21 antibodies were obtained by the method described below. In this line, LIV21 is expressed, both in the mammary tissues and in the MCF-7 cells, in the form of a doublet which migrates at an apparent molecular weight of 50 kDa.

Production of Purified anti-LIV21 Serum

The specific peptide sequences are the sequences No. 1 and No. 2.

These peptides were injected into rabbits (NZ W ESD 75 female, 2.3 kg at day 0), in agreement with standard immunization procedures, such as:

Day STEPS OF THE PROCEDURE Day 0 Collection of a control serum (20 ml) First intradermal injection O(1 ml/rabbit) 1 tube for two rabbits with 1 ml of antigen + 1 ml Freund's Complete Day 14 Second intramuscular injection (1 ml per rabbit) 1 tube for two rabbits with 1 ml of antigen + 1 ml Freund's Incomplete Day 28 Third intramuscular injection (idem D 14 Day 39 The test serum is collected (5 ml and conversed at 4° C. (serum 39) Day 49 Four subcutaneous injections (1 ml) 1 tube for two rabbits with 1 ml of ag + 1 ml Freund's Incomplete Day 60 Test serum collected (25-30 ml) and storage at 4° C. (serum 60) Day 77 Fifth intradermal injection (1 ml/rabbit) (idem D 49) Day 88 Test serum collected (5 ml and storage at 4° C. (serum D 88) Day 99 Test serum collected (25 ml) and storage at 4° C. (serum D 99) Day 102 Test serum collected (25 ml) and storage at 4° C. (serum D 102) Day 104 Test serum collected (25 ml) and storage at 4° C. (serum D 104) Day 106 Test serum collected (25 ml and storage at 4° C. (serum D 106) Day 109 Total collected by total collection of blood and storage at 4° C. (serum D 109)

The reactivity of the serum obtained was tested with respect to binding of the peptide sequences No. 1 and 2. At D60, the serum shows a good reactivity with each sequence. The serum produced 5 did not bind to any member of the E2F family.

The effect of TPA in MCF-7 cells

It has been described in the literature that TPA induces the arrest of proliferation and the differentiation of tumor cells of the MCF-7 line. In order to validate the culture conditions, the cell growth was monitored (by counting) beforehand over three days of culture in the presence or absence of TPA at a concentration of 25 nM (FIG. 13).

The cell counts demonstrate a variation in the growth kinetics between the nontreated cultures and the TPA-treated cultures. In fact, from the second day of culture onward, the number of cells is significantly different between the two treatment conditions, TPA already inducing the arrest of cell proliferation. After 3 days of treatment, the control cultures have twice as many cells as the treated cultures. TPA at the concentration of 25 nM therefore clearly inhibits proliferation under our culture conditions.

In parallel, the inventor was able to observe that the TPA-treated cells rapidly acquire characteristics of differentiated mammary gland cells (FIG. 14): hypertrophy, membrane protrusions and tendency to dissociate from one another. However, in the period of time over which the cells were studied, the secretory phenotype (appearance of granulesand of secretory canaliculi) was not observed.

FACS Analysis of the Effect of TPA

These preliminary studies of the effect of TPA showed in: S phase: The FACS study shows that the number of cells in the S phase decreases and reaches a limiting value between 12 h and 24 h of TPA treatment (FIG. 15A). However, without any further addition of TPA, the number of cells in the S phase increases again so as to return to the initial state at 72 h of treatment. G2/M phase: The number of cells in the G2/M phase increases from the beginning of the treatment, with a maximum observed at 12 hours (FIG. 15B).

GO/Gl phase: The number of cells in the GO/Gl phase is at a minimum at 6 hours and at a maximum at 24 hours (FIG. 1SC)

A maximum of cells in the S phase are therefore observed in the early periods of the kinetics (0 h to 6 h), a maximum of cells in the G2/M phase is observed at 12 h and, finally, a maximum of cells in the GO/Gl phase is observed at 24 h. Finally, without any further addition of TPA, the cells return to the S phase at 72 h.

In conclusion, these results therefore show that TPA acts rapidly on the arrest of cell proliferation and its effect on the reduction of the number of cells in the S phase is optimal at 12 h. 72 h after the single addition of TPA, the cells reinitiate the cell cycle.

The Effect of TPA on the Nuclear Localization of LIV21

The results obtained by flow cytometry led the inventor to study, in parallel, the expression of LIV21 in nuclear extracts prepared after 12 h, 24 h, 48 h and 72 h of TPA treatment (FIG. 16A). During these kinetics, maximum anti- LIV21 immunoreactivity was observed from 12 h, was maintained up to 48 h and returned toits initial intensity after 72 h of treatment. These data are to be compared with those obtained by FACS. The immunoreactivity of LIV21 significantly increases at 12 h, at which time the number of cells in the S phase is minimal. It lasts until the reinitiation of the cell cycle observed at 72 h.

Furthermore, it can be noted that this immunoreactivity is detected in the form of a single band at an apparent molecular weight of 50 kDa, whereas it was expressed predominantly in the form of a doublet in the total extracts. In order to determine the form of LIV21 to which this single band corresponds, it was compared on the same Western blot with a total extract and a nuclear extract at 12 h of treatment (FIG. 16B). The results obtained show that the nuclear form of LIV21 corresponds to the lower band of the doublet. These data suggest that the LIV21 protein might be in a different phosphorylation state according to the cell compartment.

The results of the immunocytochemical study carried out using an anti-LIV21 antibody show that the nuclear translocation of LIV21 is at a maximum at 12 h (FIG. 17) and the localization of LIV21 is predominantly cytoplasmic at 72 h, which is in agreement with the Western blotting observations. However, it is interesting to note that the expression of LIV21 already begins from 1 h of treatment in certain cells, since they are not synchronous.

All these observations show that the nuclear translocation of LIV21 is concurrent with the decrease in the number of cells in the S phase.

Example 3 Study of the Influence of on the Nuclear Translocation of LIV21

Effect of TPA on PKC& Expression

Western blotting study: Given that the protein sequence of LIV21 has putative PKC phosphorylation sites, including two specific for PKCεthe inventor tested the variation in the expression of this PKC as a function of the duration of TPA treatment. It was observed that TPA acts very rapidly on PKCE expression, which decreases from 30 min (FIG. 18). The expression of PKCzeta (PKC g) is used as an internal control since it is not sensitive to TPA.

Immunocytochemistry: In parallel, immunofluorescence experiments on treated or nontreated cultures made it possible to demonstrate this decrease in PKCε concurrent with the nuclear translocation of LIV21 (FIG. 19). It can be observed that PKCε disappears from the cytoplasm when the cells are treated with TPA and that LIV21 is detected in the nucleus.

To conclude, it is interesting to note that PKCE is weakly expressed at 12 h, at which time the fewest number of cells in the S phase and the maximum nuclear translocation of LIV21 are observed.

Example 4 Study of the Specific Role of PKCE on the Nuclear Translocation of LIV21 using a Peptide which Inhibits PKCE Function and Ttranslocation

In order to determine the specific action of PKCE on the translocation of LIV21, the cultures were treated with a peptide which is a selective antagonist of the function and the translocation of this PKC (EAVSLKPT (SEQ ID No 6)), and the results were compared with those obtained with TPA treatment. This peptide is recognized by the enzyme and binds as a modified substrate at the level of its catalytic site. It cannot be phosphorylated and acts as a specific inhibitor of the activity of PKCε.

The effect of the selective inhibition of the activity of PKCε on the nuclear translocation of LIV21 was studied by immunocytochemistry. These experiments were carried out on nontreated cultures or cultures treated for 12 h with TPA at 25 nM or with the peptide at two different concentrations, 1 and 2 μM (FIG. 20). The peptide used at the concentration of 2 μM has an effect identical to that of TPA on the nuclear translocation of LIV21.

These results were supported by cell fractionation experiments on cultures treated with the PKCE-inhibiting peptide at 2 pM, compared with TPA-treated cultures (FIG. 20 21). The same LIV21 expression profile was observed in the form of a doublet in the cytoplasm and of a single band in the nuclear fraction.

The specific inhibition of PKCE induces nuclear translocation of LIV21, thereby suggesting that LIV21 could be the target for PKCε, which would maintain it in the cytoplasm in a phosphorylated form.

Example 5 Western Blotting Analysis This example describes the conditions used for a Western blotting analysis of cancerous breast cells.

The protein extracts are heated at 80° C. for 5 minutes in a

Laemmli buffer (pH 7.4, 0.06 M Tris, 3% SDS, 10% glycerol, 1 mM PMSF, mercaptoethanol). The migration is carried out by SDS-PAGE (sodium dodecyl sulfate-polyacrylamide gel electrophoresis) 10 to 20 μg of proteins migrate in a 12% polyacrylamide gel for 1 h under denaturing conditions (migration buffer: 25 mM Tris base, 192 mM glycine, 1% SDS, pH 8.3). The proteins are then transferred onto a nitrocellulose membrane (Schleicher & Schuell) for one hour by liquid transfer, in a transfer membrane (25 mM Tris, 192 mM glycine, 20% methanol, pH 8.3). The membranes, saturated in PBS-0.1% Tween-0.1% Triton X100-5% skimmed milk for one hour, are brought into contact with the primary antibody diluted in PBS-0.1% Tween-0.1% Triton X100-1% milk at ambient temperature with gentle agitation for one hour to two hours. After washing, the peroxidase-coupled secondary antibody is incubated with the membranes for 1 h. Revelation is carried out by means of a chemiluminescence reaction using the ECL kit according to the supplier's protocol (Amersham).

The primary antibodies used are:

The anti-LIV21 serum which was produced using two synthetic peptides based on the sequence of LIV21: peptide LIV21a (SEQ ID No 1) and peptide LIV21b (SEQ ID No 2). The peptides were coupled to hemocyanin before being injected into rabbits for the immunization. The polyclonal antibody was obtained from these two peptides by having immunized two rabbits and having bled one rabbit so as to have a preimmune serum (in order to be sure that this antibody did not already exist in this rabbit).

The rabbit anti-CDK2 polyclonal antibody (Santa-Cruz technology sc-163) diluted to 1/200.

The mouse anti-p21 monoclonal antibody (Dako, M7202) diluted to 1/150.

The mouse anti-p27 monoclonal antibody (Santa-Cruz technology

sc-1641) diluted to 1/100.

The rabbit anti- PKCE polyclonal antibody (Santa-Cruz technology sc-214) diluted to 1/200.

The rabbit anti-PKC8 polyclonal antibody (Santa-Cruz technology sc-216) diluted to 1/200.

The rat anti-a tubulin polyclonal antibody (Serotec, MCAP77) diluted to 1/500.

The peroxidase-coupled secondary antibodies used (Caltag) are:

The goat anti-rabbit IgG(H+L) F(ab′)2 antibody diluted to 1/2000.

The goat anti-mouse IgG(H+L) F(ab′)2 antibody diluted to 1/2000.

Example 6

It was demonstrated that the LIV21 protein is associated with PML bodies and that, during sumoylation, LIV21 goes from a molecular weight of 50 kd to 60 kd. Colocalization of LIV21 with SUMO in the PML-SUMO/LIV21 complex was shown by immunoprecipitation (FIG. 22).

Antitumor role of PML bodies: At the proliferation stage, there are visualized modifications in the PML bodies since these PML bodies dissociate and degrade: (speckles), proteins then become available in the nucleus for ensuring transcription, proliferation, immune reactions and everything that is required for gene transcription. It has been shown that PML associates with SUMO and with HDAC-1 (histone deacetylase 1) and that its complex acts on the expression of E2F1 and PML thus acts on the arrest of proliferation by blocking E2F1. Thus, the PML/HDAC-1 complex down-regulates E2F1 expression. PML associated with Rb (p130) binds to the deacetylated histones and blocks E2F1 by binding to the chromatin (FIG. 2).

In acute promyelocytic leukemias, PML is truncated and becomes a fusion protein with the retinoic acid receptor. This fusion protein (PMLRARalpha) is due to a 15/17 chromosomal translocation. A new treatment for this disease by combining arsenic and retinoic acid in order to induce cancer cells into apoptosis has been reported in the literature. The PML protein is thought to regulate proliferation in cancers and lymphomas. The inventor has shown, by immunoprecipitation, the association SUMO-PML in which LIV21 is located.

In the above examples, it was shown that LIV21 is phosphorylated by PKCε and that TPA is an inhibitor of PKCE. The TPA-treated MCF-7 lines show an inhibition of cancerous proliferation and a cell differentiation, and LIV21 is translocated into the nucleus. If a PKCε-specific inhibitory peptide was used, it was the activity and not the expression of PKCE which was inhibited.

During this TPA treatment (25 nM), when E2F4, p130 and LIV21 were studied (green fluorescence) in the nuclei labeled (DNA) with propidium iodide (red fluorescence) (FIGS. 23 and 24), the following were observed:

after 12 h, intranuclear green fluorescence signals with the same pattern for E2F4, p130 and LIV21;

after 48 h, when the proliferation begins, E2F4 has a comparable localization; but at 72 h, it disappears from the nucleus (to the benefit of E2F1).

By observing, by double labeling, the colocalization of PML and of LIV21 at 24 h of TPA treatment (cf. merge: yellow fluorescence), it was observed that they are colocalized in the nuclei. At 48 h, the colocalization between LIV21 and SUMO is also observed (cf. FIG. 23). The hypothesis is that SUMO, which binds to LIV21, in fact targets LIV21 into the PML bodies and that LIV21 is involved in the PML/SUMO/Rb/HDAC-1 complexes.

Two different approaches were carried out in order to demonstrate that LIV21 is physically associated with PML and SUMO in the nuclear bodies, by immunoprecipitation (FIG. 22) and by colocalization by immunocytochemistry (FIGS. 23 and 24) (Rb, p130 and p107 are pocket proteins which have the same binding site). The Rb proteins repress cell growth (Fabbro, Regazzi R, Bioch Biophys Res Comm 1986 Feb. 2; 135 (1): 65-73).

When TPA is added only once, its action is exhausted after 72 h, proliferation begins again and, at this time, the PML bodies dissociate, break up and become speckles, thus leaving the proteins to ensure transcription, proliferation, etc. LIV21 is no longer located in the nucleus since it is then rephosphorylated by PKCE and thus remains located in the cytoplasm.

Example 7 Study of the Expression of LIV21 in Breast Cancer Biopsies and Skin Cancer Biopsies

In order to determine whether the observations obtained above are applicable to human tissues, a large number of skin cancer biopsies obtained from patients were studied by immunohistochemical reaction with LIV21-specific antibodies. The immunohistochemical determination of LIV21 protein expression was carried out on 60 biopsies from patients (9 patients having a biopsy of normal tissue versus a biopsy of cancerous tissue), the other biopsies corresponding to cancers which were more or less advanced and, for some, metastatic (cf. Lame superbiochips Laboratories, Seoul, Korea). Moreover, some paraffin slides from patients suffering from bladder cancer and from breast cancer were also studied.

Immunocytochemical analysis protocol:

Deparaffinize the slides.

Rehydrate the tissues.

Saturate the nonspecific sites and permeabilize the membranes.

Add the antibody in a humid chamber.

Reveal the antibody.

Deparaffinize the slides under a hood.

Two successive baths of toluene (rectapur Prolabo) 2×30 min or 2×20 min; then dehydrate the tissues with rectapur alcohol at 100% for 15 min; then rectapur ethanol at 95% for 10 min; then rectapur 70% for a further 10 min.

Thaw the antibody at the same time.

Rehydrate the tissues gently in PBS supplemented with 10% fetal calf serum and 0.1% Triton.

Saturate the nonspecific sites (for example, with ovalbumin) and permeabilize the membranes.

Rehydrate for one hour.

Deposit one ml of this “PBS” per section in order to cover the slide without it drying out at any moment (when it is a slide with cells and not tissues, half an hour is sufficient).

Place the pane and the stainless steel cover and water below so as to create a humid chamber.

Add the antibody in the humid chamber.

Dilute the rabbit serum to 1/200 in 4 ml of PBS triton, so as to continue to permeabilize the membranes, and FCS. Place 1 ml on each slide and keep away from the light and avoid evaporation.

Leave overnight or for a minimum of three hours. Then rinse with 1× normal PBS pH 7, carry out two washes of 15 to 10 min so that no trace of the first antibody remains. While preparing the

Alexa 488 green probe (in the cold at 4′ and in the dark) diluted to 1/250, therefore 10 pliter in 2.5 ml of PBS, still with 10% FCS and 0.1% Triton, rest the slides on the plate. Cover the section again with 2.5 ml in order to maintain a humid chamber for one hour, and then wash with 1×PBS, pH 7. Wash with propidium iodide at 0.5 microgram per microliter to be diluted to 20 microgram per ml and then again to 1/50, but this time, diluted in 1×PBS alone (50 microliters per 2.5 ml of PBS). Drain while taking them out of the PBS and then dispense 2.5 ml of propidium iodide over the four slides for one minute, followed by two rinses with simple PBS. Mount the slides in Moviol before reading.

All the results are summarized in Table 1 below.

TABLE 1 Expression of the LIV21 protein determined by immunohistochemistry in 50 skin cancer biopsies and 9 normal tissue biopsies “MIXED” NUCLEAR LIV21 CYTOPLASMIC LIV21 WEAKLY LIV21 TUMOR TYPE NEGATIVE POSITVE POSITIVE NORMAL TISSUES 6/9 3/9 0 FROM THE SAME PATIENTS WELL 18/21  2/21 1/21 DIFFERENTIATED CARCINOMAS MODERATELY 1/7 5/7 1/7  DIFFERENTIATED CARCINOMAS POORLY  2/11  3/11 6/11 DIFFERENTIATED CARCINOMAS CARCINOMA 0 2/9 7/9  METASTASES

For example:

FIG. 25: Results: image 43: poorly differentiated cancer; image 58: normal tissue derived from the same individual suffering from a cancer; image 40: metastatic carcinoma 10 cm and image 17: metastatic carcinoma of 3.5 cm.

FIG. 26 is, like FIG. 25, a second example of nuclear localization of LIV21 in the control and normal tissue (No. 52) of individual No. 7 suffering from a squamous cell carcinoma of the pharynx (moderately differentiated T4NOMO)

FIG. 27 is a sample of advanced bladder cancer on cystectomy (grade III urothelial carcinoma infiltrating the chorion and the musculosa) versus normal bladder tissue from the same patient with an internal control (PI): preimmune serum PI before the rabbit has been immunized against LIV21, labeling of the nuclei with propidium iodide.

FIG. 28 is a sample of breast cancer which makes it possible to demonstrate the cytoplasmic labeling of the LIV21 antibody in the cancer cells.

These results show that the cytoplasmic localization of LIV21 is an indicator of the aggressiveness and of the metastatic potential of the cancer. The detection of LIV21 expression indicates the presence of invasive, aggressive and metastatic cancer cells. These results also show that the nuclear localization of LIV21 is an indicator of normal quiescent cells, that is of well-differentiated tissues.

Example 8 Physical Interaction of LIV21 with the Proteins of the E2F Family

Coimmunoprecipitation experiments carried out using anti- LIV21, anti-E2F1 and anti-E2F4 antibodies made it possible to demonstrate that LIV21 associates with E2F4.

The members of the E2F family are transcription factors whose role has been widely described in the literature as being key molecules in the positive or negative control of the cell cycle (Slansky J E and Farnham P J 1996; Helin K 1998 and Yamasaki L, 1998), by virtue of their association with the pRb protein (Wu C L, Zukerberg L R, Lees J A 1995) or pocket proteins. E2F1 positively controls the cell cycle by transactivating the promoter of the genes responsible for cell proliferation (DNA polymerase alpha, thymidine kinase, DHFR, etc.), whereas E2F4 is described as one of the members of the EF family which negatively controls the cycle. Furthermore, a high expression of E2F1 in embryonic mammary tissues has been shown (Espanel X, Gillet G 1998), whereas it is no longer expressed in post-mitotic mammary tissues, to the benefit of a large increase in E2F4 expression (Kastner A Brun G 1998).

The identification of antigens has been carried out in cell lysates by immunoprecipitation. The analysis of the physical interaction of various proteins associated with E2F4 and E2F1 was demonstrated by coimmunoprecipitation of protein complexes.

The complex was studied using p MACS PROTEIN with MICROBEADS (MILTENYIBIOTEC). When lysates of S aureus are added, the proteins A interact with the Fe portion of the specific antibodies and the immunocomplexes become insoluble and are therefore recovered by centrifugation. After breaking of the bonds (heating) between AG/AB and protein A-rich membranes, Western blotting was carried out. These results suggest that the LIV21/E2F4 complex appears to play an important role in establishing cell quiescence.

Example 9 Functional Interaction of LIV21 with the Proteins of the E2F Family

It was demonstrated that blocking the expression of the LIV21 protein was correlated with a decrease in the expression of E2F4 and with an increase in the expression of E2F1. In parallel, the functional aspect of the increase in E2F1 was verified by studying the transcription of two of its target genes, DHFR and DNA polymerase

In conclusion, these results suggest that the LIV21/E2F4 complex acts as a complex which inhibits the expression of the E2F1 gene. This complex could correspond to a new point of control in the arrest of cell proliferation.

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What is claimed is:
 1. A method for the detection of cancer cells in a biological sample from a patient, comprising: detecting an expression product of the LIV21 gene in at least one of the nucleus and cytoplasm of cells in a sample of cells in the biological sample from the patient, the expression product of the LIV21 gene comprising a peptide sequence having 90% identity to SEQ ID NO: 4, wherein localization of the expression product in the cytoplasm is indicative of the presence of cancer cells in the biological sample.
 2. The method of claim 1, wherein the expression product of the LIV21 gene further comprises a peptide sequence having 90% identity to SEQ ID NO:
 3. 3. The method of claim 1, wherein localization of the expression product of the LIV21 gene in the cytoplasm is indicative of the presence of invasive and/or metastatic cancer cells.
 4. The method of claim 1, further comprising detecting an expression product of a gene selected from a group comprising protein kinase C epsilon (PKC_(Σ)) gene, E2F1 gene, E2F4 gene, and the HDAC1 gene, wherein localization of at least three expression products selected from the group in the cytoplasm is indicative of the presence of cancer cells in the biological sample.
 5. The method of claim 1, further comprising detecting an expression product of at least one gene selected from the group consisting of the NFkB gene, cdc2A gene, mdm2 gene, p21 gene, p53 gene, p65 gene, Ki67 gene, erk gene, CD53 gene, and CAF1 gene to determine the presence of cancer cells in the biological sample.
 6. The method of claim 1, where the expression product is the peptide sequence of SEQ ID NO:
 4. 7. The method of claim 1, wherein the expression product is detected using a specific antibody.
 8. The method of claim 1, wherein the expression product is detected by a method selected from the group consisting of Western blotting analysis, immunohistochemistry, immunocytochemistry, immunoradiography and peroxidase labeling.
 9. The method of claim 1, wherein the expression product is detected using a protein array.
 10. The method of claim 1, further comprising detecting, in the cytoplasm of the cell, an association of the expression product of LIV21 with the expression product of E2F4, and comparing the detected association with a threshold, wherein a decrease in the association from the threshold is indicative of the presence of cancer cells in the biological sample.
 11. The method of claim 1, wherein the method is used for detecting at least one of metastasized cancer, therapeutic monitoring and/or recurrences following treatment for cancer.
 12. The method of claim 1, wherein the cancer is selected from breast cancer, bladder cancer, ovarian cancer, lung cancer, skin cancer, prostate cancer, colon cancer, liver cancer, asarcoma, a leukemia and glioblastoma.
 13. The method of claim 1, wherein sequence SEQ ID NO: 4 is detected in serum as a diagnostic marker or prognostic marker for cancer.
 14. The method of claim 1, wherein the expression product of the LIV21 gene further comprises a peptide sequence of SEQ ID NO:
 3. 15. A prognostic marker or diagnostic marker for cancer comprising a peptide having 90% identity to SEQ ID NO:
 4. 16. The prognostic marker or diagnostic marker of claim 15 comprising SEQ ID NO:
 4. 17. The prognostic marker or diagnostic marker of claim 15 consisting of SEQ ID NO:
 4. 